Field of the Invention
The present invention relates to a light-emitting diode, a light-emitting diode lamp and an illumination device, and relates particularly to a light-emitting diode, a light-emitting diode lamp and an illumination device which are suited to high-brightness light emission.
Description of Related Art
Examples of known high-brightness light-emitting diodes (English abbreviation: LED) which emit red or infrared light include compound semiconductor light-emitting diodes having a light-emitting layer formed from aluminum gallium arsenide (composition formula: AlXGa1−XAs, 0≦X≦1) or a light-emitting layer formed from indium gallium arsenide (composition formula: InXGa1−XAs, 0≦X≦1). On the Other Hand, examples of known high-brightness light-emitting diodes which emit red, orange, yellow or yellow-green visible light include compound semiconductor light-emitting diodes having a light-emitting layer formed from aluminum gallium indium phosphide (composition formula AlXGa1−X)YIn1−YP, 0≦X≦1 and 0≦Y≦1). The substrates for these compound semiconductor light-emitting diodes have generally used substrate materials such as gallium arsenide (GaAs), which are optically opaque relative to the light emitted from the light-emitting layer and do not exhibit particularly high mechanical strength.
As a result, techniques for constructing junction-type LEDs have recently been disclosed with the aim of obtaining LEDs of even higher brightness, or achieving improved mechanical strength and heat dissipation properties for these devices. These techniques involve removing the substrate material that is opaque relative to the emitted light, and joining a new support substrate composed of a material that either transmits or reflects the emitted light and exhibits excellent mechanical strength and heat dissipation properties, thereby forming a junction-type LED (for example, see Patent Documents 1 to 7).